Modeling of velocities and temperatures processes distribution in the plasma-forming channel determining the design features and optimal parameters of the plasma torch nozzle is one of promising directions in development of plasma technologies. The aim of this work was to simulate the processes of velocities and temperature distribution in the plasma-forming channel and to determine the design features and optimal geometric parameters of the plasmatron nozzle  which  ensures  the  formation  of  necessary  direction  of  plasma  flows for generation of surface waves on the surface of a liquid metal droplet under the influence of the investigated instabilities.One of the main tasks is to consider the process of plasma jet formation and the flow of electric arc plasma. For obtaining small-sized particles one of the main parameters is the plasma flow  velocity.  It  is necessary that the plasma outflow velocity be close to supersonic. An increase of  the  supersonic  speed  is possible due to design of the plasmatron nozzle especially the design feature and dimensions of the gas channel in which the plasma is formed. Also the modeling took into account dimensions of the plasma torch nozzle, i. e. the device should provide a supersonic plasma flow with the smallest possible geometric dimensions.As a result models of velocities and temperatures distribution in the plasma-forming channel at the minimum and maximum diameters of the channel were obtained. The design features and optimal geometric parameters of the plasmatron have been determined: the inlet diameter is 3 mm, the outlet diameter is 2 mm.The design of the executive equipment has been developed and designed which implements the investigated process of generating droplets of the micro- and nanoscale range. A plasmatron nozzle was manufactured which forms the necessary directions of plasma flows for the formation of surface waves on the metal droplet surface under the influence of instabilities. An algorithm has been developed for controlling of executive equipment that implements the process of generating drops of micro- and nanoscale range.

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The article presents results of researches on manual arc welding efficiency development. It is proved that the arc welding inverter power source, compared with the diode rectifier, increases coefficient of transition of alloying elements into the weld joint; it also reduces the rate of alloying elements transition into slag and gaseous components and in addition reduces the harmful effects of welding on human organisms.

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The article presents the results of a theoretical study (literature review of publications), which allowed to establish the negative impact of welding aerosol (manganese and other elements) on the human body: you can use special welder protection equipment (ventilation and individual welder protection); reduce the quantitative and qualitative content of manganese welding aerosols (welding technology, power sources, modern welding materials); reduce the content of manganese in the human body, removing it with medicines. Experimental studies have shown that the use of an inverter power source, compared with a diode rectifier, contributes: to ensuring the drop-by-drop transfer of electrode metal to reduce the time of their formation by 46% and the transition by 28%; ensures the transition of alloying elements from welding materials to the weld metal by 6% and reduces its losses from the fusion line by 6% and HAZ by 3%; to reduce the intensity of education (g / min) SA and their components by 23%; to reduce the specific allocation of CA and their components by 23%.

The given work considers the influence of the power supply type (diode rectifier DR-306 and inverter Nebula-315) upon the chemical composition, microstructure, mechanical properties of weld joints and upon health characteristics of the manual arc welding process.It has been ascertained that the power supply type has a significant influence upon the weld joints properties and health characteristics of the manual arc welding process. Using a new generation inverter power supply allows less heat input into the weld bead, thus, decreasing silicium and manganese burning, improving impact resistance of weld joints under low (negative) temperature and reduces the risk of respiratory diseases for the workers.